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compute_bleu.py
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compute_bleu.py
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# Copyright 2018 The TensorFlow Authors. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
# ==============================================================================
"""Script to compute official BLEU score.
Source:
https://github.com/tensorflow/tensor2tensor/blob/master/tensor2tensor/utils/bleu_hook.py
"""
from __future__ import absolute_import
from __future__ import division
from __future__ import print_function
import re
import sys
import unicodedata
# pylint: disable=g-bad-import-order
import six
from absl import app as absl_app
from absl import flags
import tensorflow as tf
# pylint: enable=g-bad-import-order
from official.transformer.utils import metrics
from official.utils.flags import core as flags_core
class UnicodeRegex(object):
"""Ad-hoc hack to recognize all punctuation and symbols."""
def __init__(self):
punctuation = self.property_chars("P")
self.nondigit_punct_re = re.compile(r"([^\d])([" + punctuation + r"])")
self.punct_nondigit_re = re.compile(r"([" + punctuation + r"])([^\d])")
self.symbol_re = re.compile("([" + self.property_chars("S") + "])")
def property_chars(self, prefix):
return "".join(six.unichr(x) for x in range(sys.maxunicode)
if unicodedata.category(six.unichr(x)).startswith(prefix))
uregex = UnicodeRegex()
def bleu_tokenize(string):
r"""Tokenize a string following the official BLEU implementation.
See https://github.com/moses-smt/mosesdecoder/'
'blob/master/scripts/generic/mteval-v14.pl#L954-L983
In our case, the input string is expected to be just one line
and no HTML entities de-escaping is needed.
So we just tokenize on punctuation and symbols,
except when a punctuation is preceded and followed by a digit
(e.g. a comma/dot as a thousand/decimal separator).
Note that a numer (e.g. a year) followed by a dot at the end of sentence
is NOT tokenized,
i.e. the dot stays with the number because `s/(\p{P})(\P{N})/ $1 $2/g`
does not match this case (unless we add a space after each sentence).
However, this error is already in the original mteval-v14.pl
and we want to be consistent with it.
Args:
string: the input string
Returns:
a list of tokens
"""
string = uregex.nondigit_punct_re.sub(r"\1 \2 ", string)
string = uregex.punct_nondigit_re.sub(r" \1 \2", string)
string = uregex.symbol_re.sub(r" \1 ", string)
return string.split()
def bleu_wrapper(ref_filename, hyp_filename, case_sensitive=False):
"""Compute BLEU for two files (reference and hypothesis translation)."""
ref_lines = tf.gfile.Open(ref_filename).read().strip().splitlines()
hyp_lines = tf.gfile.Open(hyp_filename).read().strip().splitlines()
if len(ref_lines) != len(hyp_lines):
raise ValueError("Reference and translation files have different number of "
"lines.")
if not case_sensitive:
ref_lines = [x.lower() for x in ref_lines]
hyp_lines = [x.lower() for x in hyp_lines]
ref_tokens = [bleu_tokenize(x) for x in ref_lines]
hyp_tokens = [bleu_tokenize(x) for x in hyp_lines]
return metrics.compute_bleu(ref_tokens, hyp_tokens) * 100
def main(unused_argv):
if FLAGS.bleu_variant in ("both", "uncased"):
score = bleu_wrapper(FLAGS.reference, FLAGS.translation, False)
tf.logging.info("Case-insensitive results: %f" % score)
if FLAGS.bleu_variant in ("both", "cased"):
score = bleu_wrapper(FLAGS.reference, FLAGS.translation, True)
tf.logging.info("Case-sensitive results: %f" % score)
def define_compute_bleu_flags():
"""Add flags for computing BLEU score."""
flags.DEFINE_string(
name="translation", default=None,
help=flags_core.help_wrap("File containing translated text."))
flags.mark_flag_as_required("translation")
flags.DEFINE_string(
name="reference", default=None,
help=flags_core.help_wrap("File containing reference translation."))
flags.mark_flag_as_required("reference")
flags.DEFINE_enum(
name="bleu_variant", short_name="bv", default="both",
enum_values=["both", "uncased", "cased"], case_sensitive=False,
help=flags_core.help_wrap(
"Specify one or more BLEU variants to calculate. Variants: \"cased\""
", \"uncased\", or \"both\"."))
if __name__ == "__main__":
tf.logging.set_verbosity(tf.logging.INFO)
define_compute_bleu_flags()
FLAGS = flags.FLAGS
absl_app.run(main)